MEVINPHOS JMPR1972
Explanation
This pesticide was evaluated toxicologically by the 1965 JointMeeting
(FAO/WHO, 1965). Since this evaluation the results of someadditional
experimental work have been reported.
IDENTITY
Chemical name
dimethyl 2-methoxycarbonyl-1-methylvinyl phosphate
Synonyms
2-carbomethoxy-1-methylvinyl dimethyl phosphate, alpha isomer;
1-methoxycarbonyl-1-propen-2-yl dimethyl phosphate
Phosdrin insecticide(R), Phosdrin(R), OS-2046
In the reports provided to the Meeting several other chemical
names are used for this compound, slightly different fromthose
mentioned above.
Structural formula
Mevinphos is comprised of two geometric isomeric forms. Thecis
isomer possesses higher insecticidal activity than thetrans
isomer. At least 60% of cis-isomer is in the technical
material.
Other information on identity and properties
Analysis of a typical sample of technical mevinphos(Phosdrin(R)) gave
the following results:
% w
cis-mevinphos 62
trans-mevinphos 28
methyl aceto acetate 2
methyl-2-chloro aceto acetate 2
dimethyl methyl phosphonate 2
others (less than 1% w each) 4
100
Physical and chemical properties of technical mevinphos(Phosdrin(R))
Physical state: liquid
colour: pale yellow
Boiling range 99-103° C at 0.3 mm Hg
Vapour pressure: 1.24 x 10-4 mm Hg at 20° C
Solubility: miscible with water, acetone, carbon
tetrachloride, chloroform, ethyl-,
isopropyl- and methyl alcohols, benzene,
toluene, xylene and other highly aromatic
petroleum fractions. Slightly soluble in
carbon disulfide and kerosene.
Stability: stable under normal storage conditions.
Decomposed at high temperatures.
Hydrolysis: mevinphos is hydrolysed in aqueous The rate of hydrolosis is increased in
alkaline solutions. At room temperatureand
pH 8 the half-life of mevinphos is 21 days,
at pH 11 only 1.4 hours.
Compatibility: mevinphos is compatible with mostpesticides.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
BIOCHEMICAL ASPECTS
Absorption and distribution
Mevinphos is rapidly excreted by cattle. Milk from a cow dosed with 2
mg/kg (32P) mevinphos (80% cis, 20% trans isomer)contained 0.06
ppm after 6 hours and only 0.007 ppm after 96 hours. Milk from a cow
receiving 1 mg/kg/day for 7 days produced milk containing
approximately 0.05 ppm up to 14 days after dosage; this probably
consisted mainly of the trans isomer. Milk and tissues from
cattle receiving up to 20 ppm mevinphos in the diet for 12 weeks
contained less than 0.03 ppm (Casida et al., 1958).
Biotransformation
The main metabolite of both isomers in plants is dimethylphosphate,
although this is formed less rapidly from the trans- than from
the cis- isomer (Casida et al., 1956; Spencer and Robinson,1960).
Trans- mevinphos is degraded faster than the cis- isomer by mouse
liver homogenates; this was shown to be due to involvement of two
enzyme systems (Morello et al., 1968). The cis- isomer is
0-demethylated by a glutathione-dependent soluble enzyme, whereasthe
trans- isomer is hydrolysed at the P-O bond by a
non-glutathione- dependent enzyme (Morello et al., 1967; Hutson
et al.,1972). Cis- desmethyl-mevinphos and dimethyl phosphate
were identified in mouse liver as the main metabolites of the
cis- and trans- isomers, respectively (Morello et al., 1967;
1968).
Effects on enzymes and other biochemical parameters
The cis form is about 100 times more active than the transform in
inhibiting bovine RBC and mouse brain cholinesterases (Morello
et al., 1967).
TOXICOLOGICAL STUDIES
Special studies on reproduction
In a three-generation study, groups of 10 male and 20 female rats
received diets providing 0, 0.06 and 1.2 mg/kg body-weight/day
approximately of mevinphos (60% iso-isomer, 40%trans-isomer).
Each generation was bred twice. No effects were noted on fertility,
gestation, lactation and viability of young at the 0.06 level. In the
1.2 mg/kg group the lactation index was reduced. No gross
abnormalities were observed in the pups of these litters examined
(Estep et al., 1967).
Special studies on neurotoxicity
Technical mevinphos was administered by gavage to groups of six hens
pre-medicated with atropine sulphate and protopam sulphate. The test
group received 7.5 mg/kg on two occasions, each dose separated by an
interval of three weeks. A positive control group received
triorthophenyl phosphate (0.5 mg/kg). No signs of neurotoxicactivity
were evident in test and negative control groups. Positive controls
developed ataxia and the histological examination of the sciatic
nerve showed swollen oxons, myelin degeneration and fragmentation of
the axis cylinders (Natoff et al., 1972).
Acute toxicity
Acute toxicity of mevinphos has been studied in the rat, (Simpson
et al., 1972). Results of these studies are summarized in
Table 1.
TABLE 1
Acute toxicity of mevinphos in the rat
Material Species LD50 References
mg/kg
Technical Rat 1.4 Simpson et al.,
mevinphos 1972.
Cis-mevinphos Rat 1.4 Ibid.
Trans-mevinphos Rat 81.8 Ibid.
Short-term studies
Rat (technical mevinphos)
Groups of 12 male and 12 female rats received technical mevinphos in
the diet at 0, 0.1 and 12.5 ppm for 13 weeks. Reduction of plasma, RBC
and brain cholinesterase activities occurred in the 12.5 ppm female
group and of plasma and RBC cholinesterase activities in the male
group of the same dietary level. The male rats of this group also
exhibited slightly reduced body-weights. At the 0.1 ppm level the
exposed and control animals did not differ in relation to body-weight,
food intake, organ weights, pathology, haematology and clinical
chemistry tests (Simpson et al., 1972).
Rat (cis-mevinphos)
Groups of 12 males and 12 females received cis-mevinphos in the diet
at 0, 0.1 and 12.5 ppm for 13 weeks. Significant reductions of the
cholinesterase activity were found in the plasma, RBC and brain of
male and female rats receiving 12.5 ppm. The plasma cholinesterase
level was also reduced at 0.1 ppm, in the females only. Other
parameters were similar in the exposed and control animals (Simpson
et al., 1972).
Rat (trans-mevinphos)
Groups of 12 males and 12 females received trans-mevinphos in the
diet at 0, 10, 50, 250 and 1 250 ppm for 13 weeks. Cholinesterase
activity was significantly reduced in the plasma, RBC and brain of
females at all treatment levels, and in the males of the 250 and 1 250
ppm groups. Erythrocyte cholinesterase was also inhibited at 50 ppm in
the males. In the 10 ppm males no reductions in cholinesterase
activity were found. Body-weights and haemoglobin levels of males and
females exposed to 250 and 1 250 ppm were significantly reduced. At 1
250 ppm, food intake, organ weights and serum protein levels were
reduced, and the blood urea level and serum alkaline phosphatase
activity were increased in both sexes. Eight males and six females fed
1 250 ppm died during the test. SGPT activity was elevated at 1 250
ppm in the females only. Females at 250 ppm were found to have
increased blood urea levels and increased SGPT (Simpson et al.,
1972).
In another experiment, groups of ten males and ten females received
trans-mevinphos in the diet at 1, 5, 10, 25 and 50 ppm. Erythrocyte
cholinesterase activity was reduced in the 5, 10, 25 and 50 ppm males
and the 10, 25 and 50 ppm females. Brain cholinesterase activity was
reduced only in the 50 ppm female group. No significant changes in
plasma cholinesterase activity was found in either males or females
(Simpson et al., 1972).
Dog
Groups of four male and four female dogs received daily oral doses of
0, 0.025, 0.075, 0.25 and 0.75 mg of mevinphos/kg/body-weight for two
years. Vomiting occurred in several of the animals receiving 0.25 and
0.75 mg/kg dosages; two males in the 0.75 mg/kg group were killed
after 27 and 83 weeks dosing because of continuing vomiting and
anorexia. The general health and growth rates of the other dogs
remained unaffected throughout the study. No morphological changes
attributable to mevinphos were found in the tissue of the dogs. Plasma
and RBC cholinesterase depression were observed at 0.075 mg/kg and
higher dosages, but not at 0.025 mg/kg. After two years dosing,
inhibition of brain cholinesterase activity occurred in the 0.25 and
0.75 mg/kg females and the 0.75 mg/kg males, but not at lower dosages
(Wilson et al., 1971).
Long-term studies
Rat
Groups of 24 male and 24 female rats were given diets containing 0.37,
1.11, 3.71 and 11.14 ppm of mevinphos (60% cis-isomer) for two
years. A group of 48 male and 48 female rats acted as controls. No
differences were noted in general health, behaviour or mortality
between exposed and control animals. Transient reductions in
body-weight occurred at two higher dosage levels during the first six
months of the test. No differences in organ weight or morphological
changes occurred which could be attributed to treatment; the
haematological picture was unaltered. Experimental groups showed no
differences from controls in the number or types of tumours developing
during the two-year period. Erythrocyte and brain cholinesterase
activities were reduced at the 3.71 and 11.14 ppm levels,
respectively; lower levels did not affect the enzymes. No effects were
found on the plasma cholinesterase in the 0.37 ppm group (Simpson
et al., 1971).
OBSERVATIONS IN MAN
The effect of mevinphos on plasma and red blood cell cholinesterase
was observed in groups of volunteers (five test and two control).
Mevinphos was diluted in corn oil and administered in capsules at
dosage levels of 1.0, 1.5, 2.0 or 2.5 mg/man/day. Baseline plasma and
RBC cholinesterase levels were measured twice weekly during a
pretreatment period followed by a 30-day test period during which the
test dose was administered daily. Borderline depression (20%) in RBC
cholinesterase occurred with dose levels of 1.5 and 2.0 mg/man/day and
the highest dose produced a 24% decrease. Plasma cholinesterase was
not significantly affected at any dose level (Rider et al., 1972).
COMMENT
The data requested by the 1965 Joint Meeting has now been supplied.
Mevinphos, a mixture of cis and trans isomers is rapidly
metabolized in plants and animals. In plants, the cis isomer
disappears more rapidly than the trans isomer. The cis isomer is
more slowly degraded in animals.
In a reproduction study in rats, a reduced lactation index was
observed at 1.2 mg/kg/day, with no indications of teratogenic effects.
Studies in rats with technical, cis and trans mevinphos indicated
that the no effects for cholinesterase activity at 0.37 ppm is less
than 0.1 ppm and 1 ppm, respectively. Results showed no evidence of
carcinogenicity.
A two-year study in dogs indicated a no-effect level based upon
cholinesterase depression to be 0.025 mg/kg.
Studies in humans indicated a reduction of cholinesterase activity at
levels exceeding 1 mg/man/day.
TOXICOLOGICAL EVALUATION
Level causing no toxicological effect
Rat: 0.37 ppm in the diet, equivalent to 0.02 mg/kg
body-weight/day
Dog: 0.025 mg/kg body-weight/day
Man: 1 mg/man/day, equivalent to 0.014 mg/kg body-weight/day
ESTIMATE OF ACCEPTABLE DAILY INTAKE FOR MAN
0 - 0.0015 mg/kg body-weight
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Mevinphos is a systemic organo-phosphorous insecticide with a
relatively short action; the material has both contact and systemic
activity. It is recommended particularly for the control of a wide
range of vegetable pests, especially when applications shortly before
harvest are necessary, and for the control of aphids, leafrollers and
mites in fruit.
According to the information available, mevinphos is officially
registered and/or approved for use in
Argentina Dem. Rep. of Germany Norway
Australia Fed. Rep. of Germany Peru
Austria Greece Philippines
Belgium Hungary Portugal
Brazil Italy South Africa
Bulgaria Jugoslavia Sweden
Canada Mexico Switzerland
Colombia Morocco Tunisia
Czechoslovakia Netherlands United Kingdom
Denmark New Zealand United States
Finland Nicaragua Uruguay
France Nigeria
Use recommendations
Typical application rates for mevinphos are in the range 0.125 - 0.50
kg a.i./ha. In the United States, up to 1.0 kg a.i./ha is registered.
The recommended period between treatment and harvest varies from
country to country, but is typically between 1 and 7 days for outdoor
crops, and 7 to 14 days for glasshouse crops.
Multiple applications of mevinphos can be made, depending on pest
incidence, and use recommendations allow for these treatments.
The detailed use recommendations are given in Table 2.
TABLE 2 Recommended applications of mevinphos to crop foliage
Dosage rate
Crop Pest(s) (kg a.i/ha)
FRUIT
Pome fruit (apples, pears) aphids, mites1, scale insects 0.125 - 0.25
caterpillars, fruit flies,
TABLE 2 (Cont'd.)
Dosage rate
Crop Pest(s) (kg a.i/ha)
Stone fruit (peaches, lygus bugs, grasshoppers, mealybugs, 0.25 - 0.50
apricots, cherries) leafrollers and psyllids
Citrus (oranges, grapefruit, aphids 0.125 - 0.25
lemons) leafrollers, mites, mealybugs,
woolly whitefly2, orange tortrix3,
caterpillars, scale insects, cutworms 0.25 - 0.50
Grapes aphids 0.25 - 0.50
mites, caterpillars, leafrollers,
leafhoppers, lygus bugs 0.25 - 1.0
Strawberries aphids, spider mites 0.125 - 0.25
grasshoppers, strawberry leafrollers,
salt marsh caterpillares4 0.25 - 1.0
VEGETABLES
Brassicas (broccoli, cabbage, aphids 0.125 - 0.25
cauliflower, collards, caterpillars, bugs, mites, leafhoppers,
Brussels sprouts) leafminers, beetles, thrips 0.25 - 1.0
Spinach, lettuce aphids 0.125 - 0.25
caterpillars, mites, bugs, leafhoppers,
leafminers 0.25 - 1.0
Peas, beans aphids 1.125 - 0.25
beetles, weevils, mites, pea moth, 0.25 - 0.50
caterpillars
Cucurbits (melons, aphids 0.125 - 0.25
cucumbers) mites, caterpillars, bugs, thrips,
beetles, leafminers, leafhoppers 0.25 - 0.50
cutworm
Root, tuber and bulbous aphids 0.125 - 0.25
vegetables thrips, cutworms, caterpillars,
(carrots, potatoes, turnips mites, bugs, leafhoppers, leafminers, 0.25 - 0.50
and onions mealybugs
Tomatoes aphids, whitefly5 0.125 - 0.25
mites, fruit flies, mealybugs, 0.25 - 0.50
thrips
1 Mites are principally Tetranychidae, Tarsonemidae and Eriophyidae.
2 Aleurothrixus floccosus
3 Argyrotaenia citrana
4 Estigmene acrea
5 Trialeurodes vaporariorum and Bemisia spp.
Officially approved pre-harvest intervals
Officially approved pre-harvest intervals have been established in a
number of countries. The situation in each country is described in
Table 3. The information has been obtained principally from the
Regulatory Authorities. Every attempt has been made to have these data
current, but since legislation and regulations do change, some of
these changes may not yet be known.
With regard to pre-harvest intervals, these normally refer to an upper
application rate of 0.5 kg/ha, but since official recommendations in
some countries, especially in the case of tree fruits, are on the
basis of spray concentrations rather than rate per hectare, this upper
rate may not always be precise. At a typical spray volume in tree
fruits of 1 000 l/ha, 0.05% a.i. w/w would be equivalent to 0.5 kg
a.i./ha. In the United States, an upper rate of 1 kg/ha is now
sometimes recommended for certain row crops attacked by resistant
pests. In this case, approved pre-harvest intervals are lengthened
accordingly, as shown in Table 3. Only crops likely to be of
importance in international trade are included.
TABLE 3 OFFICIALLY APPROVED PRE-HARVEST INTERVALS
CROP COUNTRY PHI
(days)
General classes
All Hungary 5
Portugal 4
Sweden 4
Outdoor Denmark 4
Glasshouse Denmark 7
Fruit Argentina 1
Austria 14
Belgium 7
Canada 1
Canada (high rate) 3
Italy 5
Netherlands 7
Norway 7
United Kingdom 3
TABLE 3 (Cont'd.)
CROP COUNTRY PHI
(days)
Pome fruit Australia 2
Switzerland 21
Stone fruit Australia 2
Switzerland 21
Vegetables Argentina 3
Australia 2
Austria 4
Belgium 7
Brazil 4
Canada 1
Canada (high rate) 3
Colombia 10
Mexico 4
Netherlands 7
Norway 7
S. Africa 4
Switzerland 10
United Kingdom 3
Uruguay 1-4
Leafy vegetables Netherlands 7-14
Specific crops
Fruit
Apples U.S.A. - 0.25-05 kg/ha 1
Cherries " " " " " 2
Citrus Colombia 15
U.S.A. - 0.25-05 kg/ha 1
Grapes Switzerland 21
U.S.A. - 0.25-05 kg/ha 2
Peaches U.S.A. - 0.25-05 kg/ha 1
Peers U.S.A. - 0.25-05 kg/ha 1
Strawberries U.S.A. - 0.25-05 kg/ha 1
U.S.A. - 1 kg/ha 2
Vegetables
Beans Mexico 1
U.S.A. - 0.25-05 kg/ha 1
TABLE 3 (Cont'd.)
CROP COUNTRY PHI
(days)
Beet-roots West Germany 14
Broccoli, cabbage West Germany 7
U.S.A. - 0.25-05 kg/ha 1
U.S.A. - 1 kg/ha 3
Brussels sprouts West Germany 14
U.S.A. - 0.25-05 kg/ha 3
U.S.A. - 1 kg/ha 3
Carrots U.S.A. - 0.25-05 kg/ha 2
Cauliflower U.S.A. - 1 kg/ha 3
Celery Weet Germany 14
U.S.A. - 1 kg/ha 5
Collards U.S.A. - 0.25-05 kg/ha 3
U.S.A. - 1 kg/ha 7
Cucumbers(outdoors) West Germany 3
U.S.A. - 0.25-05 kg/ha 1
Cucumbers(glasshouse) Belgium 3
West Germany 4
Mexico 3
U.S.A. - 0.25-05 kg/ha 1
Gherkins Belgium 3
Mexico 3
Lettuce (outdoors) U.S.A. - 0.25-05 kg/ha 2
U.S.A. - 1 kg/ha 4
Lettuce (glasshouse) Belgium 7
Netherlands 7
U.S.A. - 0.25-05 kg/ha 10
(winter) Belgium 14
Netherlands 14
Melons (outdoors) Brazil 4
U.S.A. - 0.25-05 kg/ha 1
Melons (glasshouse) Belgium 3
Mexico 3
Onions West Germany 14
U.S.A. - 0.25-05 kg/ha 1
Peas West Germany 7
Switzerland 21
U.S.A. - 0.25-05 kg/ha 1
Peas for processing Belgium 4
Netherlands 4
Potatoes West Germany 7
U.S.A. 0.25-05 kg/ha 1
Spinach* U.S.A. 0.25-05 kg/ha 4
TABLE 3 (Cont'd.)
CROP COUNTRY PHI
(days)
Tomatoes (outdoors) Brazil 4
Colombia 8
West Germany 3
S. Africa 2
U.S.A. - 0.25-05 kg/ha 1
Tomatoes (glasshouse) Belgium 3
West Germany 4
Mexico 3
Turnips U.S.A. - 0.25-05 kg/ha 3
* Netherlands - Leafy vegetables (lettuce endive), spinach,
glasshouse summer (1 March - 1 Nov.) 7 days; winter 14 days.
RESIDUE DATA RESULTING FROM SUPERVISED TRIALS
A substantial amount of data on the residues resulting from supervised
trials was available. These trials were carried out in different
countries on food crops, especially vegetables and fruit, grown under
various conditions, using various pre-harvest intervals (PHI).
Table 4 summarizes the range of residue levels which have been found
when the product is used according to the conditions of "good
agricultural practice".
TABLE 4 Residues of mevinphos in crops following recommended foliage treatments
Maximum Minimum Range of
Crop recommended pre-harvest results
rate interval Number of Number of
(kg a.i./ha) (days) trials results (ppm)
Brassicas1 0.5 - 1.0 1 - 7 18 45 <0.01 - 0.90
Spinach 1.0 4 15 21 0.01 - 0.80
Lettuce 0.5 - 1.0 2 - 14 21 22 <0.02 - 0.50
Tomatoes 0.5 1 13 48 <0.02 - 0.20
TABLE 4 (cont'd)
Maximum Minimum Range of
Crop recommended pre-harvest results
rate interval Number of Number of
(kg a.i./ha) (days) trials results (ppm)
Cucumbers 0.5 1 - 3 10 26 <0.01 - 0.20
Peas 0.5 2 5 10 <0.05
Beans 0.5 2 7 13 <0.05 - 0.20
Root vegetables 0.5 2 4 7 <0.05
Onions 0.5 2 1 2 <0.05 - 0.10
Apples 0.5 3 8 23 <0.05 - 0.45
Pears 0.5 3 2 4 <0.02 - 0.12
Peaches 0.5 3 4 9 0.03 - 0.29
Apricots 0.5 3 2 5 <0.01 - 0.10
Grapes 1.0 3 7 20 <0.02 - 0.27
Citrus 1.0 1 6 13 <0.01 - 0.11
Cherries 0.5 3 5 14 0.09 - 0.90
Strawberries 1.0 1 8 22 <0.05 - 0.58
Melons 0.5 1 5 6 <0.02 - 0.03
1 Includes broccoli, cabbage, cauliflower, Brussels sprouts and collards.
In most cases normal dosage rates were applied in accordance with
label recommendations. However, in some experiments higher dosages are
also included. Since local recommendations, particularly regarding the
minimum pre-harvest interval, vary widely, the standard taken for
stating the ranges in Table 4 is the minimum pre-harvest interval
commonly used in practice.
In U.S.A., where both recommendations and cropping conditions are
sometimes rather different from those in other countries, ranges
deriving from commonly employed practice have been estimated on the
basis of data only from U.S.A. For guidance, the minimum pre-harvest
intervals used for deriving the ranges from the data are stated
briefly in the third column of the table. The variation in pre-harvest
interval for some of the crops is due to variation in upper dosage
rate, or whether the crops are grown under glass or not.
Detailed mevinphos residue data, obtained from supervised trials with
mevinphos on fruit and vegetables are given below. It should be noted
that:
(a) All application rates refer to active ingredient; the sum of
cis and trans mevinphos.
(b) Lbs/acre has been regarded as being essentially equivalent to
kg/ha.
Brassicas
Brassicas treated with Phosdrin according to the most extreme current
practice (i.e., for 0.5 kg/ha, PHI one day for broccoli and cabbage
and three days for cauliflower, collards and sprouts; for 1.0 kg/ha,
PHI three days for broccoli, cabbage, sprouts and cauliflower and
seven days for collards) contained residues of mevinphos in the range
of less than 0.01 ppm to 0.9 ppm, the upper figure being estimated
from the data for sprouts.
Spinach
Recommended applications of mevinphos (i.e., 0.5 kg a.i./ha, minimal
PHI four days, up to 1 kg a.i./ha, minimal PHI seven days) resulted in
residues not exceeding 0.5 ppm, four and seven days, respectively,
after the final application.
Lettuce
The basis for deriving the range of residues from non-U.S.A. data was
that of current recommendations in the Netherlands, and U.S.A. data is
that of current recommendations. On this basis the range of residue
levels reported was from <0.02 - 0.50 ppm.
Under all these conditions, it has been shown that the residues of
mevinphos did not exceed 0.50 ppm, when label recommendations were
followed, i.e. PHI for lettuce grown outdoors was 4-7 days and for
glasshouse lettuce 7-14 days, depending on application rate and
growing period. In winter, the longer PHI's are recommended.
Beans
Residues of mevinphos did not exceed 0.05 ppm (maximum dosage rate of
0.5 kg a.i./ha) when beans were treated with 0.5 kg/ha mevinphos and
sampled two days later.
Peas
Residues of mevinphos did not exceed 0.05 ppm in peas which had
received recommended treatments of mevinphos (maximum of 0.5 kg
a.i./ha), sampled two days after application.
Root vegetables, bulbs and tubers
With a final treatment to harvest interval of two days, mevinphos
residues in carrots, turnips, onions and potatoes did not exceed 0.10
ppm, following recommended applications of mevinphos (maximum dosage
rate of 0.5 kg a.i./ha).
Tomatoes
At a dosage rate of up to 0.50 kg a.i./ha, and an interval between the
final application and harvest of one day, residues of mevinphos ranged
from less than 0.02 ppm to 0.08 ppm; at the double dosage rate, i.e.
up to 1 kg a.i./ha, residues ranged from 0.05 - 0.2 ppm.
Cucumbers
In cucumbers grown under glass, three days after application of
mevinphos at a maximum dose of 0.5 kg a.i./ha, residues did not exceed
0.13 ppm. Similarly, in cucumbers grown outdoors, residues were less
than 0.10 ppm one day after recommended applications.
Melons
Residues of mevinphos in whole melons did not exceed 0.05 ppm one day
after the final treatment at a maximum of 0.5 kg a.i./ha.
Gherkin
After recommended applications at a maximum of 0.5 kg a.i./ha,
residues did not exceed 0.1 ppm after a PHI of three days in gherkins
grown under glass.
Top fruit
Studies with mevinphos on top fruit are summarized in Table 5.
TABLE 5 Mevinphos residues on fruit
Maximum Pre-harvest Residues
Fruit treatment interval (ppm)
(kg a.i/ha) (days)
Apples 0.5 3 0.45
Pears 0.5 3 0.14
Peaches 0.5 3 0.29
Apricots 0.5 3 0.10
Cherries 0.5 3 0.90
Citrus 1.0 1 0.11
Grapes
At an application rate of 1.0 kg a.i./ha and a PHI of three days, the
maximum residue of mevinphos in grapes was 0.27 ppm.
Strawberries
Following applications of mevinphos to strawberries grown outdoors at
a maximum rate of 1.0 kg a.i./ha, with a minimum PHI of one day, the
maximum residue was 0.14 ppm; at a slightly higher treatment level,
i.e. 1.25 kg a.i./ha, the maximum residue was 0.45 ppm.
FATE OF RESIDUES
General comments
Mevinphos residues in crops decrease rapidly, partly due to
volatilization and partly through degradation. The principal
degradation products are dimethyl phosphate and acetoacetic acid.
Provided mevinphos is used according to the conditions of good
agricultural practice, detectable residues will not occur in meat,
milk and milk products. Livestock is unlikely to be exposed to
mevinphos residues in feed since crops used for animal feeds are
rarely treated. Nevertheless, data are available to show that cattle
eating feed containing high levels of mevinphos do not produce meat or
milk containing appreciable residues.
In animals
Casida et al. (1958) conducted studies with mevinphos fed to cattle
at levels of up to 20 ppm, expressed on the dry matter content (far in
excess of levels which could occur in practice). From the results of
these studies, the authors stated that mevinphos had no tendency to
accumulate in any tissue, but was rapidly detoxified in the animal.
Feeding of 32P-labelled mevinphos for seven consecutive days to a cow
at a level of 40 ppm, in dry matter, did not lead to levels of
mevinphos in whole milk above 0.06 ppm at any time during the study.
Mevinphos residues in the tissues from this cow at autopsy at the end
of the seven-day period were essentially found only in the liver (0.3
ppm) and kidneys (0.04 ppm).
In a more extensive experiment, 12 lactating cows were fed for a
12-week period at levels of 1, 5 and 20 ppm on the total diet. Samples
of milk were taken periodically and samples of fat, liver, kidney,
muscle, heart and brain at the end of the feeding period from all
treatments. All contained less than 0.03 ppm mevinphos (limit of
determination of the analytical method).
However, their experiments showed that in the case of the cis-isomer
of mevinphos, dimethyl phosphate was the main degradation product
together with very small amounts of mevinphos acid (the free
carboxylic acid). In the case of the trans-isomer, the same products
were found, although there was even less of the carboxylic acid.
Desmethyl derivatives (where the methoxyl groups joined to the P atoms
would have been hydrolysed to hydroxyl groups) were not detected.
In plants
Casida et al. (1956) reported that after applying mevinphos to
vegetable crops as a foliar spray, 90% of the amount applied was lost
within two days and 99% in four days. From experiments in which pea
and bryophyllum plants absorbed 32P-labelled mevinphos through their
roots, it may be concluded that within 12 hours after application
losses occurred primarily through volatilization, whereas thereafter
decomposition made the greater contribution. Using similar methods
with labelled mevinphos applied to cucumber, maize, bean and pea
seedlings, they reported that the cis-isomer declined more rapidly
than the trans-isomer.
Spencer and Robinson (1960) grew pea seedlings in gravel and applied
32P-labelled mevinphos via the roots. Like Casida et al. (1956)
they found that the trans-isomer degraded somewhat more slowly than
the cis-one. This conclusion is further supported by those field
residue studies by Shell where cis- and trans-isomers were
analysed separately.
When pea plants were exposed to labelled cis-mevinphos acid instead
of mevinphos, degradation of the acid was somewhat slower than that of
cis-mevinphos. Moreover, although dimethyl phosphate was still the
main degradation product, desmethyl mevinphos acid was also formed.
For these reasons, the main degradation pathway of mevinphos acid was
also formed.
For these reasons, the main degradation pathway of mevinphos must have
been direct to the dimethyl phosphate and could not have been
primarily via the carboxylic acid.
In soil
In soil, mevinphos appears to be decomposed primarily by chemical
hydrolysis (Hindin, 1963). Getzin and Chapman (1959) studied the fate
of 32P-labelled mevinphos in soil and the subsequent uptake in pea
plants by an enzyme inhibition method. There is a positive correlation
with organic matter content and base-exchange capacity.
Most mevinphos was held by peat (127 mg/100 g soil) and least by sand
(3-8 mg/100 g soil).
In sand, the residues in peas reached 170 ppm after two days,
decreasing to 8.5 ppm after 14 days; in muck soils, the residues in
the pea plant were 0.82 ppm and 0.05 ppm, respectively, after the same
periods.
Residues after harvest
The comparatively rapid decline in mevinphos residues seen in the
growing crop usually continues after harvest whilst the commodity is
being stored or transported to the market. Thereafter, the various
commercial and domestic processes reduce levels still further, often
to below the limits of analytical determination. Consequently,
residues at harvest bear little relation to residue levels in food
when it is ready to eat. At the latter point, mevinphos residues often
may not be detectable, even though residues near the proposed
tolerance levels were present at harvest time.
Residues in crops stored under ambient conditions
Studies have been undertaken in which samples of fruit and vegetables
have been stored at ambient temperatures for 2 - 9 days. Table 6
summarizes typical figures for the decline in residues in cabbage,
broccoli, cauliflower, lettuce and spinach stored in ambient
conditions (Shell Research Ltd., 1957, 1971, 1972; Shell Chimie,
1972).
TABLE 6 Decline of residues in leafy vegetables after harvest
Time Residues of mevinphos (ppm)
(days) Red cabbage Broccoli Cauliflower Lettuce Spinach
Harvest 0.2 0.27 0.06 0.15 0.35 8.7
2 0.11 0.09 <0.02 0.10 0.30 5.2
4 0.06 0.02 - 0.05 0.20 2.7
6 0.02 - - - - 1.1
8 - <0.02 - - - -
9 0.01 - - - - -
Comparable data for fruits were also obtained and are summarized in
Table 7.
TABLE 7 Decline of residues in fruits after harvest
Residues of mevinphos (ppm)
Time (days) Apples Peaches Strawberries
Harvest 0.72 1.29 2.9 0.34 0.11
2 - - - 0.25 0.04
3 - - 2.7 - -
6 0.07 - - - -
9 - 0.21 - - -
Effect of deep-freeze storage
Laws (1959) studied the effect of deep-freeze storage on residues of
mevinphos in cabbage; samples were taken after six weeks and six
months of deep-freeze storage. Practically no decrease of mevinphos
residues occurred during these storage periods.
Effects of domestic processing
The data shown in Table 8 are representative of those available for
the effect of washing in cold water (Shell Research Ltd., 1972; Shell
Development Co., 1962).
TABLE 8 Mevinphos residues in leafy vegetables after washing
Crop Initial residues Residues after washing
(ppm) (ppm)
Spinach 1.10 0.54
0.96 0.66
0.50 0.35
Cabbage 0.11 0.03
0.02 <0.01
Broccoli 1.60 0.72
0.14 0.10
Cauliflower 1.00 0.09
0.74 0.52
0.09 0.05
In general, the lower initial residues were derived from produce which
had been stored under ambient conditions. In some cases the
proportionate loss after washing was less from crops containing lower
than from those containing higher residue levels.
A study by Wit (1972) demonstrated that household washing and
subsequent cooking of endive resulted in a loss of 50% of the residue
occurring in the crop at the retailer. In lettuce, household washing
removed about 48% of the initial residue. Data are given in Table 9.
TABLE 9 Mevinphos residues in vegetables after washing and cooking
Vegetable Average residue, 4 replicates (ppm)
initial residue after washing after cooking
Endive 0.12(0.08-0.15) 0.10(0.02-0.16) 0.06(0.03-0.09)
Lettuce 0.54(0.36-0.80) 0.28(0.24-0.30)
Whilst the residue data used as the basis for proposing tolerances
were based on the crops as picked, many crops, especially lettuce and
brassicas, are trimmed before cooking. Table 10 gives data which show
the difference between residues in the outer leaves and the trimmed
produce and which are typical of all available data. In general outer
leaves represent 10-20% of the weight of the untrimmed crop (Shell
Research Ltd., 1957, 1960, 1971; Shell Chimie, 1971).
In melons, 75-90% of mevinphos residues were found to be present in
the rind. Peeling reduced levels in cucumbers and peaches by up to
50%, in apples by up to 60% and in pears by between 50 and 75%. In
citrus, residues were confined primarily to the peel, and where
residues were reported in peel, they were usually below 0.01 ppm in
the pulp (Shell Development Co. 1957, 1958; Shell Chimie, 1970; Shell
Research Ltd., 1957, 1972; Shell Chemical Co., 1961).
Cooking vegetables and fruits reduces residues as illustrated by the
data given in Table 11 (Shell Research Ltd., 1960, 1972).
TABLE 10 Residues of mevinphos in outer leaves and trimmed crop
Crop External leaves Trimmed crop
(ppm) (ppm)
Lettuce 0.50 0.40
0.24 0.20
0.17 0.12
Cabbage 0.59 <0.05
0.50 0.08
0.08 <0.02
0.64 0.02
0.22 0.02
Brussels sprouts 0.63 0.08
0.25 0.16
0.02 <0.02
TABLE 11 Mevinphos residues in crops after cooking
Residues (ppm)
Crop Before cooking After cooking
Broccoli 0.09 0.02
Cabbage 0.03 0.01
Spinach 2.70 0.81
1.10 0.36
Beans 15.01 7.40
TABLE 11 (cont'd)
Residues (ppm)
Crop Before cooking After cooking
Apples 1.10 0.59
0.65 0.26
0.60 0.43
1 Spiked sample.
Blanching and canning
In the canning of fruit and vegetables, which involves considerable
heat treatments, virtually all mevinphos residues are eliminated.
A study by Dormal et al. (1959) demonstrated that blanching and
canning spinach, peas and beans effectively removed all residues of
mevinphos. Similar studies also showed the complete elimination by
commercial canning of residues of mevinphos present at harvest on
spinach and peaches; 40% of the residues of mevinphos present were
removed from beans purely by the process of blanching, while this
reduction was increased to 99% on subsequent bottling (Shell Research
Ltd., 1960, 1971; Shell Chemical Co., 1957).
Processing of wine
Painter et al. (1959) added mevinphos to grape must, and residues of
mevinphos were found in wine prepared from the must. Measurable
amounts of mevinphos were also retained in the sediment.
Mevinphos residues in certain crops after harvest
Whilst canning effectively removes residues from treated crops, the
effects of the milder domestic processes are variable and the
available data are summarized under individual crop headings.
Where possible an estimate is made of the level which could be
expected in the food when ready to eat if the crop were at the
proposed tolerance level at harvest. In the great majority of cases,
harvest time levels will be well below the proposed tolerances, so
that the estimate made here for residues at the point of consumption
will in general be well above those occurring in practice.
Brassicas
The combined effects of delay between harvest and marketing, washing,
removal of outer leaves and cooking are likely to reduce harvest
residues of about 1.0 ppm to a maximum of 0.05 ppm.
Spinach
The combined effects of washing, transport and cooking would be
expected to reduce harvest residues of about 1.0 ppm to around 0.15
ppm.
Peas, beans, carrots, turnips and potatoes
Residue levels observed at harvest where crops had been treated
according to good agricultural practice were invariably less than 0.05
ppm, and no processing work was undertaken in these crops.
Apples, pears, peaches, apricots, cherries and strawberries
The principal losses of residue in fruits occur during transport to
the market. Such factors as peeling, washing and cooking are not
always relevant and are not considered here. In estimating losses
there are great variations in the times and conditions of transport.
Thus, apples and pears from distant countries may experience shipment
periods of several weeks whereas fruits such as cherries and
strawberries may be eaten within a matter of days after harvest. Thus,
in the case of apples it is probable that residues at the
proposed-tolerance level could decline to below the limits of
determination where long shipment periods are involved. In the case of
strawberries which reach the market in two days, residues could
decline to between 50% and 70% of their harvest values.
Melons and citrus fruit
These fruits are peeled before being eaten. Residues in melons of 0.05
ppm at harvest would not be likely to contain detectable levels in the
edible portion. The same is true of citrus fruit.
Lettuce
Some reductions in residues will occur between harvest and consumption
due to transport and removal of outer leaves. Washing will also have
some effect (residues decline by washing about 50%). Precise figures
of residue losses between harvest and the moment of consumption are
difficult to estimate, especially in view of the widely varying
conditions and times of transport from one country to another.
METHODS OF RESIDUE ANALYSIS
Residues of mevinphos are best determined by gas-liquid
chromatography. Alternatively, an enzyme inhibition cholinesterase
method may be employed.
Gas chromatographic methods
Because of their accuracy, specificity, sensitivity and speed, gas
chromatographic methods of analysis are the methods of choice.
Mevinphos can be determined by using a flame photometric detector
(Beroza and Bowman, 1968; Brody et al., 1966). A specific method for
the analyses for residues of both the cis and trans isomers of
mevinphos has been developed (Shell Research Ltd., 1957-72) and
satisfactorily used on crops down to a general level of 0.01 ppm for
each isomer. The crops are extracted by maceration with chloroform.
Low water content crops are dampened with water before extraction.
Co-extracted natural products can be removed by cleanup using a liquid
- liquid chromatographic technique, followed by analysis of the
mevinphos-containing extract Using this procedure, mean recoveries of
80-115% from crops at the 0.02 - 0.20 ppm level may be achieved for
each isomer.
A thermionic detector has also been employed in the analyses of crops
for residues of mevinphos (Winterlin, 1970; Shell Chemical Co., 1969).
The crops are extracted with either ethyl acetate or chloroform,
followed by a column adsorption chromatographic cleanup, if required,
and determination by GLC equipped with a thermionic flame detector.
This provides a quick and sensitive means for the detection, as well
as the separation of the two isomers of mevinphos. These thermionic
detector methods are capable of detecting levels of mevinphos as low
as 0.01 ppm, with recoveries in the range of 90% to 110%.
Enzyme inhibition
A specific enzymatic method for the detection and determination of
mevinphos in crops and animal products has been developed (Shell
Development Co., 1964). The samples for analysis are extracted with
chloroform, transferred to water, and determination is effected by a
standard enzyme inhibition spectrophotometric method. Using this
procedure, the limit of determination of mevinphos is 0.02 ppm for
crops, 0.01 ppm for milk and up to 0.10 ppm for animal tissue.
Recoveries are in the range of 80% to 110%.
Bioassay Methods
Bioassay methods have been described but such techniques have now been
largely superseded.
NATIONAL TOLERANCES
Officially approved tolerances for mevinphos have been established in
some countries. The information presented in the following table has
been obtained principally from the regulatory authorities. Every
attempt has been made to present the most recent data, but the
following list is not a fully authentic one. The figures in table 12
refer to the sum of cis and trans mevinphos.
APPRAISAL
Mevinphos is a systemic, rather volatile organo-phosphorous
insecticide, which is used on a considerable scale in many countries,
especially on vegetables and fruit, for the control of a wide range of
pests, such as aphids, leafrollers and spider mites. This pesticide is
recommended, particularly when control of pests is necessary, a
relatively short time prior to harvest.
Technical mevinphos contains no less than 60% of the cis-isomer of
mevinphos, and about 28% of trans-isomer. The former possesses
considerable higher insecticidal activity than the latter.
The principal impurities in the technical material are methyl
acetoacetate, methyl-2-chloro acetoacetate and dimethyl methyl
phosphonate (each of the components mentioned comprise about 2% by
weight of the total technical mevinphos).
Mevinphos is mainly used as an emulsifiable liquid. The concentration
rates of use range from 0.125-0.5 kg a.i./ha., applied as a foliage
spray; in U.S.A. up to 1 kg a.i./ha. is registered to accommodate
extreme pest conditions.
The residue data available were obtained from many countries with
different climatic and growing conditions and those presented are,
with a few exceptions, representative of levels likely to occur at
harvest under conditions of good agricultural practice.
Information is available on the fate of mevinphos residues in animals,
in plants and in soil; residue data on animal tissues and products of
animal origin, such as milk, show that residues occur only from
feeding levels far in excess of those which are likely to occur in
practice. Provided mevinphos is used according to conditions of good
agricultural practice, no measurable amounts of residue will occur in
meat, milk and milk products.
TABLE 12 Examples of national tolerances reported to the meeting1
Country Crop(s) Tolerance
(ppm)
Argentina peas, beans, cucumbers, citrus 0.25
lettuce, melons, apples, pears, grapes 0.5
brassicas, spinach, cherries, peaches 1.0
and plums
Australia fruits and vegetables 0.25
(recommended)
Belgium spinach 0.3
other vegetables, fruit 0.1
Brazil peas 0.25
lettuce 0.5
broccoli, spinach, turnips 1.0
Canada all treated crops 0.25
Czechoslovakia leafy vegetables, cabbage 0.1
Fed. Rep. of spinach 0.3
Germany vegetables and top fruit 0.1
other crops 0.05
Hungary all crops 0.1
Yugoslavia apples 0.5
crops other than apples 0.1
Netherlands spinach 0.3
other vegetables, fruit 0.1
Switzerland vegetables )
top fruit ) 0.25
grapes )
South Africa tolerances vary according to crop 0.25 - 1.0
U.S.A. citrus, peas, beans, cucumbers, root veg. 0.25
apples, pears, grapes, lettuce, melons 0.5
stone fruit, brassicas, strawberries 1.0
1 Additional tolerances may exist in some countries for crops grown
for local consumption. These tolerances do not appear.
When mevinphos was applied to plants, it was shown that it decreased
rapidly within 12 hours after application, primarily through
volatilization; thereafter degradation was mainly responsible for
decrease in residue levels, the principle degradation products being
dimethyl phosphate and acetoacetic acid.
Little information is available on mevinphos residues in foods in
commerce.
A number of methods for residue analysis based on gas chromatographic
procedures are available for specific determination of mevinphos
cis-and trans-isomers. The GLC methods of analysis are the methods
of choice, based on accuracy, specificity, sensitivity and speed.
Recommendations are given for the most appropriate extraction
procedures for residues in crops. These procedures can be used and
adapted for regulatory purposes as required.
The limit of determination of the GLC methods mentioned is as low as
0.01 ppm for both cis- and trans-mevinphos in crops, with
recoveries in the range of 90 - 110%.
Alternatively, an enzymatic method for the detection and determination
of mevinphos residues may be used. The limit of determination of the
latter method is 0.02 ppm of mevinphos (both isomers) for crops, 0.01
ppm for milk and 0.1 ppm for animal tissue. Recoveries are in the
range of 100 - 110%.
Various rates of application and pre-harvest intervals occur in
different countries. It has been demonstrated that considerable losses
of residues available at harvest occur whilst the commodity is being
stored or transported to market. Thereafter, various commercial and
domestic processes reduce levels still further, often below the limits
of determination. Consequently, residues at harvest bear little
relation to residue levels in food at the time of consumption.
RECOMMENDATIONS
TOLERANCES ppm
Brassicas (broccoli, Brussels sprouts, cabbage,
cauliflower, collards) cherries, strawberries. 1
Lettuce, spinach, apples, grapes, peaches. 0.5
Cucumbers, tomatoes, apricots, citrus fruits, pears. 0.2
Carrots, beans, onions, peas, potatoes, turnips 0.1
Melons 0.05
FURTHER WORK OR INFORMATION
NONE
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